On January 9, 2019, Gloria announced that he would run for Mayor of San Diego in the 2020 election. In announcing his campaign, he focused on housing affordability, homelessness, and climate change, and promised to build a "world class public transportation system."[2]

Gloria is a third generation San Diegan, all four of his grandparents having moved to San Diego because of their involvement with the military.[3] He has described his ethnic background in an interview as being: "[b]asically half Native American (Tlingit-Haida, an Alaskan tribe), a quarter Filipino and then a little bit of Dutch and Puerto Rican."[3]

He grew up in the Clairemont neighborhood and attended Madison High School. He was interested in politics from childhood. At age 10, he was runner-up in a "mayor for a day" contest. At 14, he volunteered to work for Democratic candidates in the 1992 election.[4]

U.S. Congresswoman Susan Davis has been his political mentor ever since they first met in 1993, when Gloria was a high school freshman and Davis was the director of the Aaron Price Fellows Program, a San Diego leadership program for high school students focused on civic education and cross-cultural understanding.[5] In 2002, Gloria became Davis's district director,[5] a position he held until being elected to the city council in 2008.[6]

While working for Davis, Gloria also served as a San Diego Housing Commissioner from 2005 until 2008. Openly gay, he is also a former chairman of the San Diego LGBT Community Center and was a resident panelist on San Diego's Prostitution Impact Panel.[7]

Gloria ran for the District 3 seat vacated by the termed-out Toni Atkins in the 2008 election. He received a plurality of votes in the June 2008 primary election, leading to a November run off election against fellow Democrat Stephen Whitburn, a former journalist, community activist and ally of then District 6 councilmember Donna Frye.[7][8] Gloria defeated Whitburn with 54.3% of the vote.

Gloria was chair of the city's Budget and Finance Committee from 2011 to 2016. Gloria represented San Diego on the San Diego Metropolitan Transit System Board and SANDAG, where he chaired the transportation committee.[11] In December 2012, at its first meeting after new members took office, Gloria was unanimously elected to serve as Council President, replacing retiring President Tony Young.[12]

Upon the resignation of Mayor Bob Filner on August 30, 2013,[13] Gloria became the interim mayor of San Diego, with limited powers.[14] This made San Diego the second largest city in the United States (after Houston) to have an openly gay mayor at that time.[15][16] He served until March 3, 2014, when mayor-elect Kevin Faulconer was sworn in. While serving as interim mayor, he remained the city councilmember for District 3 and retained the title of city council president; however, City Council President Pro Tem Sherri Lightner carried out the duties of the council president.[17] Gloria was considered a possible candidate to replace Filner, but chose not to run.[18]

As interim mayor, Gloria reversed several of Filner's actions. In September 2013, he ordered city police and zoning code officers to resume enforcement actions against medical marijuana shops; in one of his first actions as mayor, Filner had ordered city staff to stop such enforcement.[19] He also announced the city will re-hire lobbying firms in Sacramento and Washington that Filner had fired.[20] He ordered that public records be made more quickly and easily available to citizens, in contrast to the cumbersome centralized process established by Filner.[21]

On December 10, 2014, the city council voted 4–5 on a motion of whether to reappoint Gloria as council president for the new term, with Sherri Lightner joining the four council Republicans to defeat the measure. The council then voted 7-2 to appoint Lightner as council president, with Gloria and David Alvarez in opposition.[22]

On April 7, 2015, Gloria announced that he would run in 2016 for the California State Assembly78th district seat held by Assembly Speaker Toni Atkins, who was termed out. Gloria was immediately endorsed by Atkins and by Sarah Boot, who had earlier announced her own candidacy for Atkins' seat, but withdrew upon Gloria's announcement.[23] On November 8, 2016, Gloria was easily elected over his relatively unknown Republican opponent with the second-highest margin of victory in San Diego County.[24] He was easily re-elected in 2018 with over 70 percent of the vote in both the primary and the general election.

Shortly after assuming office in 2016, Gloria was chosen by Speaker Anthony Rendon to join democratic leadership in the assembly as assistant majority whip.[25] In January 2018, he moved up in leadership to the position of majority whip.[26]